This invention relates generally to an attachment for a shop tool that enable a shop person to form a set of precision holes, which are spaced apart from each other as well as in alignment with each other without having to invest in an expensive line bore machine. The concept of standalone line bore machines for forming a set of precision holes is known in the art. Typically, line bore machines are a specialty tool used to form a set of blind or through holes for receiving dowel pins, which may for example be used to support a shelf. One type of line boring machine, which is sold by Delta Machinery, comprises a standalone apparatus having an integral power source and a workhead containing a set of drills that are rotatingly supported in the line bore machine. In operation, of the Delta Machinery standalone line bore machine a workpiece is placed below a set of rotating drills that extend outward from an integral workhead. Next, one lowers the rotating drills into the workpiece to simultaneously drill a set of holes that are fixedly spaced from each other as well as in alignment with each other. While such line bore machines work well the infrequent use and the cost of the standalone line bore machine makes it financially unfeasible for a person with a home workshop or small business to purchase a standalone line bore machine. For example, a person, who has a home work shop, may want to build a single piece of furniture that requires a set of precisely aligned and spaced holes that are to receive dowel pins which will be used to support shelves. The cost of the line bore machine for occasional or limited home workshop use or limited small business use makes the purchase of a line bore machine impractical. On the other hand the home workshop owner needs a reliable and accurate device to form such holes or the article will have an inferior appearance.
An alternate less expensive method for a hobbyist or a person with a home workshop or small business is to use a drill guide that contains a set of precisely aligned and spaced holes that form a template for drilling a set of precision holes. Typically, one clamps the drill guide to the workpiece and then uses a hand drill or drill press to drill a set of aligned and spaced holes by successively inserting a rotating drill bit into each of the openings in the drill guide. Although such a guide is an inexpensive alternative to a standalone line bore machine it requires care in setting up and aligning the drill guide, particularly if the number of drilled holes exceeds the number of guide holes in the drill guide. In addition, it is easy for an axis of the holes drilled with a hand drill to be misaligned from a perpendicular condition since each of the holes are drilled separately without the assistance of an axis guide. Unfortunately, a misalignment in the axis of the holes may result in a subsequent misalignment of a dowel pin located therein, which not only detracts from the appearance of the article but may also provide an uneven shelf support if the holes are used for supporting dowel pins.